Entering and Exiting Awareness are Asymmetrical: Evidence from tracking Continuous Flash Suppression

This study provides a model for obtaining cleaner threshold estimates of entry into and exit from conscious awareness measured with the popular breaking continuous flash suppression (bCFS) and newer tracking CFS (tCFS) paradigms. In both, a suppressed target increases in contrast until it breaks into awareness. tCFS also measures exit thresholds by reversing the contrast change. Both CFS paradigms require a response when the threshold is reached and thus involve a reaction-time component. During this period, target contrast continues to change and threshold estimates are inflated (the "overshoot" problem). Here, we measure reaction-time components for both increasing (entering awareness) and decreasing targets (exiting awareness). We find overshoot is asymmetrical, being greater for stimuli entering (breakthrough thresholds) than for exiting awareness (suppression thresholds). To solve "the overshoot problem", we introduce a mathematical model that quantifies reaction-time components so they can be partialled out to produce clean breakthrough and suppression thresholds. The model can also be applied to previously published CFS studies. The model works for simple target detection and two-alternative target discrimination, even in the continuous tracking paradigm of tCFS. With the timing corrections applied, changes in pupil diameter around transitions in awareness are shown to align with the corrected time points, most clearly when targets exit awareness. Even after correction, the contrast decrease required for a target to exit awareness was greater than the increase required for it to enter awareness.